Using claims data from the Health Care Cost Institute, the researchers found that average in-network rates for two categories of common mental health services in commercial and Medicare Advantage plans in 2014 were 13% to 14% less than fee-for-service rates in traditional Medicare.

That contrasts with the private plans paying up to 12% more than traditional Medicare for similar evaluation and management services provided by other types of physicians, according to the study published in Health Affairs.

Federal and state laws require insurers to cover behavioral health services in parity with physical healthcare, but low payment rates could jeopardize those patient access gains, the authors said.

Parity’s promise may remain unfulfilled if patients cannot access in-network providers,” wrote Daria Pelech and Tamara Hayford of the CBO. “Mental health providers might not contract with insurers if they view payments as too low, especially if out-of-network payments are higher.”

Even as private plans paid lower rates, enrollees spent more out of pocket because they went out of network for mental health services more than six times as often as for other types of services.